Method and apparatus for early detection of kicks

ABSTRACT

The present disclosure relates to a method for early kick detection in a drilling system with a drilling fluid loop, comprising: collecting flow-in rate and flow-out rate of a drilling fluid; calibrating the flow-out rate to obtain a calibrated flow-out rate of the drilling fluid; determining a flow rate difference between the flow-in rate and the calibrated flow-out rate of the drilling fluid; and identifying the kicks based on the flow rate difference. The present disclosure also relates to an apparatus for early kick detection in a drilling system with a drilling fluid loop.

BACKGROUND

Embodiments of the disclosure relate generally to methods and apparatus for early kick detection in a drilling system with a drilling fluid loop.

During drilling operations, gas, oil or other well fluids at a high pressure may flow from the drilled formations into the wellbore created during the drilling process. An unplanned influx from the formation into the wellbore is referred to in the industry as a “kick” and may occur at unpredictable moments. If the “kick” is not promptly controlled, the well and the equipment in the well will be damaged. Currently, specific commercial meter, such as Coriolis, EM or Doppler meters may be used for the flow-in and flow-out measurement in an uphole environment; or using the difference between flow-in and flow-out, which is obtained by collecting more information and constructing more complex models to calibrate as much as possible of the flow-out measured in a downhole environment, to detect the kick.

Therefore, it would be desirable if a method and an apparatus could be provided for early kick detection at least with simple configuration, high reliability and efficiency.

BRIEF DESCRIPTION

In accordance with one embodiment disclosed herein, a method for early kick detection in a drilling system with a drilling fluid loop is provided. The method comprises collecting flow-in rate and flow-out rate of a drilling fluid; calibrating the flow-out rate to obtain a calibrated flow-out rate of the drilling fluid; determining a difference flow rate between the flow-in rate and the calibrated flow-out rate of the drilling fluid; and identifying the kicks based on the flow rate difference.

In accordance with another embodiment disclosed herein, an apparatus for early kick detection in a drilling system with a drilling fluid loop is provided. The apparatus comprises a first sensor, positioned in a onshore input flow section of the drilling fluid loop, for detecting flow-in rate of a drilling fluid; a second sensor, positioned in an undersea return flow section of the drilling fluid loop, for detecting flow-out rate of the drilling fluid; and a controller communicated with the first sensor and the second sensor. The controller comprises a parameter collecting unit configured for collecting the flow-in rate and the flow-out rate of the drilling fluid; a calculating unit configured for calibrating the flow-out rate to obtain a calibrated flow-out rate of the drilling fluid and determining a flow rate difference between the flow-in rate and the calibrated flow-out rate of the drilling fluid; and a kick detection unit configured for identifying the kicks based on the flow rate difference.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and aspects of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic diagram of an apparatus for early kick detection in a drilling system with a drilling fluid loop according to one embodiment; and

FIG. 2 is a flow diagram of a method for early detection of kicks in a drilling system with a drilling fluid loop according to one embodiment.

DETAILED DESCRIPTION

Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The use of “including,” “comprising” or “having” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

A “fluid” may be, but is not limited to, a gas, a liquid, an emulsion, a slurry, and/or a stream of solid particles that has flow characteristics similar to liquid flow. “Fluid pressure” is a pressure generated by a fluid in a formation.

Referring to FIG. 1, an apparatus for early detection of kicks in a drilling system with a drilling fluid loop according to one embodiment is shown. In this illustrated embodiment, the apparatus 1 is useable in an offshore drilling installation having a drilling fluid loop 11 into a well drilled below the seabed. A fluid flow is pumped into the well from a platform on the water surface and flows towards the well via an input fluid path. A return flow flows from the well towards the surface via a return path. In one embodiment, as shown in FIG. 1, the platform on the water surface is a mud tank.

In this illustrated embodiment, the apparatus 1 includes a first sensor 10 configured to measure the flow-in rate of a drilling fluid pumped into the well. The first sensor 10, positioned in a onshore input flow section 101 of the drilling fluid loop 11, may be a stroke counter connected to a fluid pump that provides the input flow into the input fluid path. Due to the uniformity of the density and other physical properties of the fluid input into the well, various known flow measuring methods may be employed.

The apparatus 1 further includes a second sensor 20 configured to measure the flow-out rate of the drilling fluid. The second sensor 20, positioned in an undersea return flow section 102 of the drilling fluid loop 11, may be a flow measuring device of any existing type with no requirement for the accuracy of the measured flow rate.

The apparatus 1 further includes a controller 30 communicated with the first sensor 10 and the second sensor 20. The controller 30 comprises a parameter collecting unit 31, a calculating unit 32 and a kick detection unit 33.

The parameter collecting unit 31 is configured for collecting the flow-in rate and the flow-out rate measured by the first sensor 10 and the second sensor 20 in real time.

The calculating unit 32 is configured for calibrating the flow-out rate and determining a flow rate difference between the flow-in rate and the calibrated flow-out rate of the drilling fluid. The calculating unit 32 further includes a modeling element 321 and a calibrating element 322. The modeling element 321 is configured for monitoring an evaluation of the flow-in rate and the flow-out rate over time, and obtaining a reference pattern based on the evaluation of the flow-in rate and the flow-out rate over time. The calibrating element 322 is configured for determining the calibrated flow-out rate based on the reference pattern. For illustration purpose, a linear function of the trend of the flow-in rate and the flow-out rate as measured over time is now assumed as flows (It is understood that the trends of the flow-in rate and the flow-out rate over time may be a higher-order function or a non-linear function):

VFR _(out)(t)=K·VFR _(in)(t−T ₀)  (1)

wherein VFR_(in) is the flow-in rate as measured, VFR_(out) is the flow-out rate as measured, t is time, K and T₀ is time-varying parameters which can be estimated via the following equation:

min{sum(|VFR _(out)(t)−K·VFR _(in)(t−T ₀)|)}  (2)

In normal operation (i.e., no kick event occurs), the flow-out rate equals to the flow-in rate and should be understood as a calibrated flow-out rate (

_(out)), then the following equation can be obtained:

_(out) =VFR _(in)  (3)

By replacing the equation (3) into the equation (1), the following equation can be obtained:

VFR _(out)(t)=K·

_(out)(t−T ₀)  (4)

Then, the calibrated flow-out rate may be obtained via the equation (4).

After the calibrated flow rate is obtained, the flow rate difference may be determined by the following equation (5):

Wherein the flow-in rate (VFR_(in)) can be constant or variable. If the flow-in rate is constant, the above calibration process may be simplified via the following equation:

T ₀=0

VFR _(out)(t)=K·VFR _(in)

The kick detection unit 33 is configured for identifying the kicks based on the flow rate difference. Specifically, the flow-out rate always equals to the flow-in rate during normal operation (i.e., no kick event occurs), and the flow rate difference is zero. If the flow-in rate continues to be greater than zero, the flow rate difference continues to increase, which indicates that a kick event has occurred or is imminent.

The controller 30 further includes a pre-processing unit (34) configured for pre-processing the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) of the drilling fluid to filter out fluctuations so as to increase the accuracy of the preceding calibration process.

In some embodiments, the apparatus 1 also includes a third sensor 40 configured for collecting drilling parameters of drilling bit motion. The drilling parameters include the area of the cross section of the drilling bit and the rate of the drilling bit motion. The third sensor 40 is communicated with the Wellsite Information Transfer Specification System, and the controller 30 as well. In the preceding calibration process, the variety of the flow-out rate caused by the drilling bit motion also needs to be taken into consideration. The variety of the flow-out rate caused by the drilling bit motion may be obtained by the following equation:

VFR _(out) _(drillingbit) (t)=S·drillingbitvelocity(t)

Wherein S is the area of the cross section of the drilling bit, drillingbitvelocity is the rate of the drilling bit motion, and VFR_(out) _(drillingbit) (t) is the flow-out rate caused by the drilling bit motion.

Referring to FIG. 2, a flow diagram of a method for early detection of kicks in a drilling system with a drilling fluid loop according to one embodiment is illustrated. The method 100 includes a step 110 of collecting flow-in rate and flow-out rate of a drilling fluid; a step 120 of calibrating the flow-out rate to obtain a calibrated flow-out rate of the drilling fluid; a step 130 of determining a flow rate difference between the flow-in rate and the calibrated flow-out rate of the drilling fluid; and a step 140 of identifying the kicks based on the flow rate difference.

In one embodiment, the step 120 includes a step 121 of monitoring an evaluation of the flow-in rate and the flow-out rate over time; a step 122 of obtaining a reference pattern based on the evaluation of the flow-in rate and the flow-out rate over time; and a step 123 of determining the calibrated flow-out rate based on the reference pattern. The reference pattern comprises at least one time-varying parameter for calibrating the flow-out rate.

In one embodiment, the method 100 further includes a step 150 of pre-processing the flow-in rate and the flow-out rate of the drilling fluid to filter out fluctuations.

In one embodiment, the 100 further includes a step 161 of collecting a drilling parameter of drilling bit motion; and a step 162 of estimating a drilling flow-out rate based on the drilling parameter to calibrate the flow-out rate.

The apparatus and method as described above are provided for early kick detection. An accurate estimation of a flow-out rate can be obtained without a high precision flowmeter and a complicated calibration process of the flow-out rate so as to achieve accurate and early detection of kick.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional assemblies and techniques in accordance with principles of this disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

What is claimed is:
 1. A method for early kick detection in a drilling system with a drilling fluid loop, comprising: collecting flow-in rate (VFR_(in)) and flow-out rate (VFR_(out)) of a drilling fluid; calibrating the flow-out rate (VFR_(out)) to obtain a calibrated flow-out rate (

_(out)) of the drilling fluid; determining a flow rate difference (Δflow) between the flow-in rate (VFR_(in)) and the calibrated flow-out rate (

_(out)) of the drilling fluid; and identifying the kicks based on the flow rate difference (Δflow).
 2. The method of claim 1, wherein calibrating the flow-out rate (VFR_(out)) to obtain the calibrated flow-out rate (

_(out)) of the drilling fluid comprises: monitoring an evaluation of the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) over time; obtaining a reference pattern based on the evaluation of the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) over time; and determining the calibrated flow-out rate (

_(out)) based on the reference pattern.
 3. The method of claim 2, wherein the reference pattern comprises at least one time-varying parameter (K, T₀) for calibrating the flow-out rate.
 4. The method of claim 1, further comprising: pre-processing the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) of the drilling fluid to filter out fluctuations.
 5. The method of claim 1, further comprising: collecting a drilling parameter (S, drillingbitvelocity) of drilling bit motion; and estimating a drilling flow-out rate (VFR_(out) _(drillingbit) ) based on the drilling parameter (S, drillingbitvelocity) to calibrate the flow-out rate (VFR_(out)).
 6. An apparatus for early kick detection in a drilling system with a drilling fluid loop, comprising: a first sensor, positioned in a onshore input flow section of the drilling fluid loop, for detecting flow-in rate (VFR_(in)) of a drilling fluid; a second sensor, positioned in an undersea return flow section of the drilling fluid loop, for detecting flow-out rate (VFR_(out)) of the drilling fluid; and a controller communicated with the first sensor and the second sensor and comprising: a parameter collecting unit configured for collecting the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) of the drilling fluid; a calculating unit configured for calibrating the flow-out rate (VFR_(out)) to obtain a calibrated flow-out rate (

_(out)) of the drilling fluid and determining a flow rate difference (Δflow) between the flow-in rate (VFR_(in)) and the calibrated flow-out rate (

_(out)) of the drilling fluid; and a kick detection unit configured for identifying the kicks based on the flow rate difference (Δflow).
 7. The apparatus of claim 6, wherein the calculating unit comprises: a modeling element for monitoring an evaluation of the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) over time, obtaining a reference pattern based on the evaluation of the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) over time; and a calibrating element for determining the calibrated flow-out rate (

_(out)) based on the reference pattern.
 8. The apparatus of claim 7, wherein the reference pattern comprises at least one time-varying parameter (K, T₀) for calibrating the flow-out rate.
 9. The apparatus of claim 6, further comprises: a pre-processing unit configured for pre-processing the flow-in rate (VFR_(in)) and the flow-out rate (VFR_(out)) of the drilling fluid to filter out fluctuations.
 10. The apparatus of claim 6, wherein the parameter collecting unit is further configured for collecting a drilling parameter (S, drillingbitvelocity) of drilling bit motion from a third sensor; and the calculating unit is further configured for estimating a drilling flow-out rate (VFR_(out) _(drillingbit) ) based on the drilling parameter (S, drillingbitvelocity) to calibrate the flow-out rate (VFR_(out)). 